Lasers have been used to spot weld one article to another. However, when articles such as coexpansive sleeves are to be spot welded to each other, problems can arise. When two sleeves are spot welded to each other a plurality of sites in a sequential manner, it is often difficult to maintain alignment between the sleeves to better than one micron, often a required accuracy. One possible reason for this is that sequential spot welding of the sleeves can result in thermal distortion thereof, causing relative movement between the sleeves.
A proposed solution to overcome the movement problem is to simultaneously spot weld the sleeves at two opposed sites using suitably directed beams emanating from both ends of a single laser. To avoid uneven heating of the sleeves, the beams must have substantially identical power and intensity profiles. To satisfy this criterion, additional costs are incurred for two sets of energy monitors, shutters, beam-expanding telescopics and fixtures. A pair of beams can also be derived from a single laser beam using conventional beam-splitting technology and equalizing techniques. Conventional equalizing techniques can result in an enery loss of up to forty percent, thus requiring a more powerful, and hence more expensive, laser to accomplish a given welding operation.
Accordingly, there is a need for a cost-effective welding system that provides two matching beams having substantially identical power and intensity profiles.